What sort of blood test is a BAL?

BAL stands for "Blood alcohol content", so the most basic answer to this question is that it is a test that tests for the content of alcohol in your blood. The units in which it gives the result of this test is usually in percentage of the blood that is alcohol at the time of the test. The most common way of testing for the BAC of somebody is a breathalyzer, which is most often used by police who are testing to see if a driver is over the legal limit of BAC, which is .08 if you are over 21 in most states in the U.S.